Aftercooler bypass means for a locomotive compressed air system

ABSTRACT

Method and apparatus for heating gases cooled by an aftercooler that receives hot gases from a compressor. The method includes the steps of directing at least a portion of said hot gases to means for bypassing the aftercooler, and using the bypass means to direct hot gases to a location that receives cooled gases from the aftercooler. The hot gases are used at the location to heat the cooled gases when ambient temperature is at or below freezing, and are used downstream from the aftercooler when moisture freezes in the aftercooler.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of co-pending patentapplication Ser. No. 09/902,192 filed Jul. 10, 2001 now U.S. Pat. No.6,644,934, which is a divisional of Ser. No. 08/897,277 filed Jul. 21,1997 now U.S. Pat. No. 6,283,725.

FIELD OF INVENTION

The invention relates generally to locomotive air compressors andaftercoolers used to substantially reduce the temperature of highpressure air exiting the compressor, and particularly to a means forpreventing downstream freezing of condensate in the high pressure airwhen outside ambient conditions are at or below freezing.

BACKGROUND OF INVENTION

U.S. Pat. No. 5,106,270 to Goettel et al., and assigned to the assigneeof the present invention, shows an integral compressor and aftercoolerthat is extremely efficient in cooling hot, high pressure discharge airfrom a compressor. When the compressor is operating under a heavy dutycycle the air temperature is reduced to within 20° of ambienttemperature. If the compressor is running in a start/stop manner under alight duty cycle, the temperatures of the heated gases from thecompressor can be reduced to temperatures within 5° of ambient. Withsuch efficiency it is quite possible for moisture contained in theaftercooler or in the discharge air from the aftercooler to freeze whenoperating under freezing conditions.

SUMMARY OF THE INVENTION

The present invention provides a means to increase airstreamtemperatures flowing from an aftercooler to essentially remove thepossibility of freezing prior to reaching a reservoir of pressurized airor bypass the aftercooler altogether should freezing occur in theaftercooler. The reservoir is typically fitted with a heated drain valvethat removes (drains) condensate from the reservoir. The freezingproblem is solved by bypassing the aftercooler with at least a portionof the hot air issuing from the compressor and directing the hot air toexhaust piping of the aftercooler. If the aftercooler freezes, all hotair is bypassed. In either case, warm air is supplied to the reservoir.

In one embodiment of the invention, by-pass of the aftercooler can beeffected by a pipe connected between the compressor and aftercoolerexhaust. The pipe provides a constant volume of hot, compressed air flowfrom the compressor to the aftercooler exhaust.

In another embodiment of the invention, a three-way valve is used to mixgases exhausting from the high pressure head of the air compressor andfrom an aftercooler to provide the warmer airstream. In bothembodiments, condensate is prevented from freezing in the aftercoolerexhaust and thus remains in liquid form long enough to reach thereservoir and the heated drain valve.

The three-way valve can be operated by sensing either the main reservoirinlet temperature or more simply ambient air temperature. Thus, innonfreezing conditions, the three-way valve directs all high pressureair through the aftercooler so that it can be cooled and any moisturetherein condensed. If, on the other hand ambient temperature falls belowa certain level, the three-way valve is operated by temperature sensingmeans to bypass at least a portion of the high pressure air leaving thecompressor.

OBJECTS OF THE INVENTION

It is, therefore, one of the primary objects of the present invention toprovide a method and an apparatus to prevent freezing of condensate inhigh pressure air before it reaches a main reservoir in a locomotive andtrain braking system.

Another object of the present invention is to provide a method and anapparatus which provides a constant low volume flow of hot exhaust gasesfrom a compressor directly to aftercooler exhaust piping, theaftercooler being connected to receive the major portion of hot gasesfrom the compressor for cooling.

Yet another object of the present invention is to provide a method andan apparatus using a three-way valve that is effective in bypassing anaftercooler when freezing temperatures are sensed.

In addition to the various objects and advantage of the inventiondescribed above, various additional objects and advantages of theinvention will become more readily apparent to those persons skilled inthe pneumatic art from the following more detailed description of theinvention, particularly, when such description is taken in conjunctionwith the attached drawing Figures and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic side elevation view of a compressor providedwith a pipe for by passing hot gases to an aftercooler exhaust,

FIG. 2 is a diagrammatic front elevation view of the compressor andby-pass pipe of FIG. 1,

FIG. 3 is a schematic representation of a three-way thermostaticallycontrolled valve providing a mixing application of aftercooler andcompressor discharge gases,

FIG. 4 is a sectional view of a three-way valve and thermostat (inelevation) that can be used in the three-way valve of FIG. 3,

FIG. 5 is a schematic diagram showing a three-way valve operated by amagnet valve under control of a temperature signal, and

FIG. 6 shows an embodiment wherein the three-way valve is located at theinput side of the aftercooler.

BRIEF DESCRIPTION OF A PRESENTLY PREFERRED AND VARIOUS ALTERNATIVEEMBODIMENTS OF THE INVENTION

Prior to proceeding to the much more detailed description of the presentinvention, it should be noted that identical reference numerals are usedthroughout the several views illustrated in the drawing figures todesignate identical components, having identical functions, for the sakeof clarity and understanding of the invention.

Referring now to diagrammatic FIG. 1, an aftercooler 10 is shownconnected to a source of hot high pressure compressed air, such as thehigh pressure cylinder 11 of the multi-cylinder compressor 1, which isshown in the above referenced Goettel et al. patent. In the Goettel etal Patent, hot high pressure air enters an aftercooler to be reduced intemperature for the purpose of condensing water vapor contained in theair to liquid water before the air is used to operate the brakes of arailroad train. As discussed earlier, when operating a compressor andaftercooler in cold temperatures, freezing of water in exhaust piping 12of the aftercooler can take place. Moisture may also freeze in theaftercooler. If the amount of water in the high pressure air issubstantial and freezes, it can block aftercooler tubing and exhaustpiping such that the pressurized air needed for brake operation is notavailable. The aftercooler supplies the reduced temperature, highpressure air to a main reservoir or reservoirs 14, in FIG. 3, on alocomotive where liquid water is drained from the reservoir before thepressurized air is made available for operating the brakes of the train.

The present invention provides a means to increase airstream temperaturebefore reaching reservoir 14 to avoid the freezing problem while stillreducing substantially the water content in brake air. The reservoir 14itself is typically provided with a heated drain (not shown) so thatcondensate can be removed even under freezing conditions.

In one embodiment of the invention, air stream temperature in piping 12is increased by use of a simple bypass pipe 16 connected to highpressure cylinder 11. Pipe 16 bypasses aftercooler 10 to outlet fittingand pipe 12 such that a portion of hot gases from cylinder 11 aredirected to the fitting and pipe 12, the amount of hot gases by-passeddepending on the internal size of the pipe. The major portion of the hotgases are sent directly to aftercooler 10, via a pipe 18 in FIG. 2, forcooling. Pipe 18 is connected to a header 20 (FIG. 1) on the input sideof the aftercooler. A second header 21, visible in FIGS. 3 to 5, feedscooled gases to exhaust outlet and pipe 12.

Pipe 16 provides a limited but substantially constant flow of hot gasesto exhaust pipe 12, which gases then mix with the cooled gases exitingaftercooler 10, in pipe 12, to warm the same and thereby preventfreezing of condensate in the cooled gases when ambient temperature isat or below freezing. The aftercooler, of course, provides the bulk ofthe high pressure air for brake operation, which air is substantiallyfree of water, as the aftercooler reduces air temperature to condensewater vapor in the high pressure air to liquid water for draining fromreservoir 14.

A safety valve 19 is, as shown in FIG. 2, connected to a center “T”fitting 19A that divides hot gas flow from cylinder 11 between pipe 16and pipe 18. The safety valve 19 is employed to release air toatmosphere at a certain air pressure in fitting 19A. If moisture freezesin aftercooler 10, the internal diameter of pipe 16 provides a constantflow of hot gases from cylinder 11 sufficient to prevent operation ofthe safety valve 19, all of the compressed air now bypasses theaftercooler and flows directly to the reservoir 14. The supply ofcompressed air is thereby uninterrupted and safety of the train is intact, as compressed air is available for braking.

In another embodiment of the invention, air stream temperature isincreased by use of a three-way valve 22 that allows bypassing ofaftercooler 10, in the manner shown in the drawings FIGS. 3 to 5. InFIG. 3, a first port 23 of valve 22 is located to receive compressed airdirectly from compressor 1, via a pipe 24, while a second port 25 of thevalve 22 is connected to receive cooled air from the aftercooler via apipe 26. In this manner heated gases flow from valve 22 through a thirdport 27 of the valve 22 to piping 12 leading to reservoir 14 whilecooled air with condensate also flows to and through the third port 27to pipe 12 and the reservoir 14. The hot gases from the compressorthereby warm the cooled gases from the aftercooler to insure a gastemperature above freezing when the gases enter the reservoir 14.

The amount of hot gases needed to insure against freezing in pipe 12 isnot substantial and is controlled by the sizes of the port orifices 23and 25 in valve 22 relative to the pressures of the hot gases issuingfrom compressor cylinder 11 and the cooled gases exiting aftercooler 10.

In operating in abient conditions above freezing, valve 22 can be“closed” to the hot output of the source of hot compressed air so thataftercooler 10 can perform its normal and efficient function of coolingall of the hot gases received from the source of hot compressed gases.When ambient temperature falls to freezing, valve 22 is operated in an“on” position for at least partial bypassing of aftercooler 10. Thevalve 22 can be internally thermostatically operated (FIG. 4) to startthe mixing process by opening port 23 when temperatures fall tofreezing. When temperatures rise above freezing, the thermostat moves toa position to close port 23 so that valve 22 receives only aftercoolergases through valve port 25 for transfer to pipe 12 and reservoir 14.

Valve 22 can operate in a variable manner by use of a thermostat 18(FIG. 4) located in the valve 22, i.e., the amount of mixing in thevalve 22 to maintain an appropriate temperature in pipe 12 can be madedirectly proportional to ambient temperature. Thus, the colder thetemperature outside the valve 22 the more the thermostat closes to theaftercooler to allow more hot air to mix with the aftercooler exhaustpipe 12. In FIG. 6, hot air flow from compressor 1, enters valve 22 viapipe 24, and flows through a small opening 23A in the valve 22 whenambient temperature falls toward freezing (and below). From opening 23A,air flows through a cylinder 28A of thermostat 28 to exhaust pipe 12.When ambient temperature is above freezing, cylinder 28A closes offopening 23A.

FIG. 5 of the drawings shows an embodiment of the invention in whichvalve 22 can be operated externally by use of a magnet valve 30pneumatically connected to valve 22 by a pipe 31. Magnet valve 30 iselectrically operated by a switch 32 connected to a valve operatingmagnet 34. Valve 30 is connected to receive air pressure from the sourceof the hot compressed air via a pipe 36 which the magnet valve 30 usesas control air to operate three-way valve 22. When switch 32 receives afreezing temperature signal or a close to freezing signal, the switch 32closes to apply an appropriate voltage to magnet 34. Magnet 34 isenergized to operate magnet valve 30 in a manner that applies the airpressure received from the source of hot compressed air to three-wayvalve 22 to open the same to the hot gases in pipe 36. Hot gases thusjoin with the cooled gases that enter three-way valve 22 to heat thesame. When ambient temperature rises above freezing, switch 32 is openedto deenergize magnet 34 and valve 30 so that three-way valve 22 returnsto a condition that closes the three-way valve 22 to the hot gasesthereby allowing only cooled gas flow to reservoir 14.

Switch 32 can be operated by temperature signals originating at alocation remote from the switch 32. Locomotives generate and usetemperature measurements for a variety of reasons. The measurements areusually converted to digital signals for use by computers located in thecabs of locomotives. Switch 32 can be operated by such a digital signalto effect the operation of valve 30.

In another embodiment of the invention (FIG. 6) three-way valve 22 canbe located on the “entry” side of aftercooler 10. Again, valve 22 can beoperated in the manners described above to bypass aftercooler 10 andthereby prevent freezing of condensate in pipe 12 when ambientconditions are freezing, and restoring the aftercooler to receive thefull output of hot gases from a source of hot gases when ambient risesabove freezing.

While the presently preferred embodiment for carrying out the instantinvention have been set forth in detail above, those persons skilled inthe brake control art to which this invention pertains will recognizevarious alternative ways of practicing the invention without departingfrom the spirit and scope of the claims appended hereto.

1. An apparatus for heating gases cooled in an aftercooler connected toreceive hot gases from a compressor, the apparatus comprising: (a) meansconnected to receive a portion of such hot gases from such compressorfor directing said portion of said hot gases around such aftercooler andto a predetermined location receiving cooled gases from suchaftercooler, while a remainder of such hot gases is sent to suchaftercooler from such compressor for cooling, such hot gases beingeffective to heat such cooled gases at such receiving location; (b) atemperature sensitive means for controlling an amount of hot gasesby-passed around such aftercooler and to such location for receivingcooled gases from such aftercooler, wherein said temperature sensitivemeans is a thermostat located in a three-way valve connected to receiveboth hot and cooled gases.
 2. The apparatus, according to claim 1,wherein said temperature sensitive means includes an electrical switchconnected to receive a temperature representing signal.
 3. Theapparatus, according to claim 2, wherein a magnet valve is connected toreceive hot gas from such compressor for operating said bypass means,with said electrical switch being connected to said magnet valve foroperating said magnet valve in response to receipt of a temperaturerepresenting signal.
 4. The apparatus, according to claim 1, whereinsaid bypass means includes a three-way valve having two ports connectedrespectively to receive hot gas from such compressor and cooled gas fromsuch aftercooler, and an outlet port for directing a mixture of suchgases from said valve.
 5. The apparatus, according claim 4, wherein saidthree-way valve supplies a mixture of such gases to an output pipe whenambient temperature falls to at least one of near freezing and freezing.6. The apparatus, according to claim 4, wherein said apparatus furtherincludes a magnet valve connected to receive hot compressed gas fromsuch source of such gas, and use same as a control gas for operatingsaid three-way valve.
 7. The apparatus, according to claim 6, whereinsaid apparatus further includes a switch electrically connected to amagnet of said magnet valve for controlling energization anddeenergization of said magnet based upon temperature signals received bysaid switch representing ambient, freezing and above freezingtemperatures.
 8. The apparatus, according to claim 1, wherein saidapparatus further includes a temperature sensitive means for controllingan amount of hot gas by-passed around such aftercooler and to suchpredetermined location for receiving such cooled gas from suchaftercooler.
 9. A method of by passing an aftercooler connected toreceive high temperature compressed air from a source of such air, themethod comprising the steps of: (a) connecting (1) a first port of athree-way valve to such source of high temperature air, (2) a secondport of such valve to such aftercooler, and (3) a third port of suchvalve to an output pipe; (b) opening said valve between said first andsecond ports to conduct high temperature air through said valve to saidthird port when ambient temperature is near, at or below freezing, andto close said valve when ambient temperature is above freezing; (c)using a magnet valve provide control said three-way valve for operatingsaid three way valve in response to changes in ambient temperature. 10.The method, according to claim 9 wherein said method includes additionalstep of using a thermostat located in said three-way valve to open andclose said valve.